(1) Field of the Invention
The present invention relates to a method for inhibiting the growth of bacteria in a raw or cooked processed meat at temperatures above freezing and at near neutral pH's with an inorganic propionate salt thereby extending the shelf life of the meat. The present invention relates to preferred compositions including a bacteriocin which are useful in the method. In particular the present invention relates to the use of low levels of a sodium propionate or calcium propionate salt, and preferably the bacteriocin, in the processed meat, such as beef, poultry or fish and mixtures thereof, for this purpose.
(2) Prior Art
The prior art has used propionate salts in various processed foods. Examples are U.S. Pat. No. 3,899,594 to Nickerson et al and British Patent application No. 1,562,568, filed Mar. 12, 1980, and British Patent Application No. 1,275,480. The propionates are used in low pH foods, less than pH 6.0. British Patent No. 1,275,480 indicates that the propionate salts require a low pH to be effective. It had not been thought that the propionate salts would be useful against bacteria at low levels in higher pH processed meats at temperatures above freezing probably because propionates, considered to be mycostats, are not effective against mold at high (greater than 5.3) pH. British Patent No. 1,562,568 describes the use of sodium propionate in frozen meats as a mycostat at pH 5.5 to 7.0 without any specific amounts being disclosed. Freezing greatly reduces the risk of microbial growth and also reduces the taste of the meat. Woolford and Anderson, Food Industries 17:622 (1945) describes the use of propionates in various foods for inhibiting various bacteria and molds, but not in meats at temperatures above freezing.
U.S. Pat. No. 4,883,673 to Gonzalez describes the use of bacteriocins in foods. The bacteriocins are not described as useful with propionates.
The shelf life of packaged (canned or fresh packaged) processed meat products is limited by bacterial spoilage. This spoilage is caused primarily by gram-negative bacteria and secondarily by lactic acid producing bacteria. One solution to this problem is to freeze the product during distribution to inhibit spoilage. This practice detracts from the fresh concept of the product and taste, increases the product cost and is a problem if there is a failure in the freezing. It would be preferred to refrigerate the meat preferably at between about 4.degree. C. to 12.degree. C. A method is needed for slowing the growth of pathogens at these temperatures in meat.